The goals of this proposal are to a) elucidate in further detail the intermolecular associations of proteins of the human erythrocyte membrane skeleton; b) determine how membrane proteins assemble during erythroid development; c) use the erythrocyte membrane as an experimentally accessible model system for understanding membrane structure and function in more complex cells. An additional, new area of interest is the mechanism of invasion of human erythrocytes by P. falciparum malarial parasites. As a general approach, these studies will be performed with membrane proteins that have been purified and characterized, and associations between these proteins will be evaluated quantitatively. Specific projects are in the following areas: 1) Studies of binding of erythrocyte anykrin and proteolytic fragments of ankyrin in solution to defined oligomeric states of spectrin and the cytoplasmic domain of band 3. 2) Studies of a newly discovered calmodulin-binding protein that is a component of the erythrocyte membrane skeleton with goals of determining its protein associations, and regulation of these associations by calcium and calmodulin. 3) Evaluation of the RBC as a model system to study protein associations in receptor-mediated endocytosis, using clathrin that has recently been purified from RBC cytosol, and transferrin receptor from placenta. 4) Studies of heretofore uncharacterized erythrocyte proteins including purification, nearest neighbor analysis and search for isoforms in other tissues. Candidates will be band 4.2, a membrane skeletal form of band 7 and a recently discovered calmodulin-binding protein. 5) Assembly of an erythroid membrane skeleton during differentiation of erythroleukemia cells. 6) Studies of the mechanisms of invasion of human erythrocytes by merozoites of P. falciparum, with emphasis on purification of merozoite proteins that interact with band 3.